The gypsum wallboard industry produces wallboard through a process designed to ensure an effective adhesive bond between two external layers of heavy caliper paper that enclose an interior gypsum plaster core. The industry traditionally has added large quantities of starch binder to the plaster core in order to promote adhesion to the paper shell. The industry also adds a large excess of water to the plaster so that, during drying of the plaster between the two paper layers, the excess water can migrate from the wet plaster into the paper carrying starch binder along with it to establish bonding of the plaster to the paper surface. However, such a process is highly energy-intensive due to the amount of drying energy required to migrate and evaporate the excess water from the gypsum plaster core.
There is general industry need for reducing the amount of water used in the production of wallboard since drying costs have increased substantially for the gypsum wallboard producers. It is also apparent that a reduced plaster to water ratio can be attainable with the present invention that can in turn result in a higher strength wallboard. This strength enhancement, attained by including the paper surface treatment in the gypsum wallboard manufacturing process, in turn optionally could allow the production of stronger, low density, wall board products.
It has unexpectedly found that an alternative to the use of starch and high water ratio in the wet plaster core can be practiced and yet still achieve strong bond between the paper layers and the plaster core.